This invention generally relates to a center-pivot irrigation system of the towable type. Generally, such systems are similar in operation, but are shorter in length, than the standard center-pivot system which may be as much as a quarter of a mile long and longer. A towable system is used where it is desirable to irrigate more than one section of land with a single center-pivot system, thus requiring the towing of the system from one location to another.
Towable systems have long been known in the art and generally include a main conduit extending generally radially from a central pivot location. The conduit is supported along its length by a series of self-propelled support towers which travel on wheels driven to move in generally circular paths about the pivot location. Sprinklers are spaced along the conduit to dispense the liquid onto the field to be irrigated.
Unlike standard center-pivots wherein the end of the conduit at the pivot is attached to a substantially permanent support structure, a towable system must have an assembly at the pivot that effectively pivotally anchors and supports the system during operation in irrigating the field, but which may be readily disengaged from its ground support and its liquid supply and adapted for towing the entire system to a new location.
Examples of structures heretofore used to anchor and support a towable system at the pivot location have been generally tripod type structures mounted on wheels, with the tripod structure remaining pivotally stationary as the system operates. In such assemblies the conduit is connected to the tripod structure by a swivel connection.
There have been a number of disadvantages associated with such prior structures. The pivot assemblies are substantially different in structure than the other support towers used in the system and are generally heavier and more massive, with associated disadvantages in cost, inventory, and the like. Because the pivot support remains stationary during operation of the system, the conduit and the wheels of the support towers may not be in proper alignment with the wheels of the pivot support for towing the system, thus requiring that the pivot support be "jockeyed" into proper alignment in relatively close quarters and usually on wet ground. Also, because the entire pivot support structure is free to pivot relative to the rest of the system, it may be impractical to tow the system from the outer end of the conduit. Such pivot assemblies are usually wider than the remaining support towers with resultant excessive crop loss in moving the system.
Such prior systems also require collector rings at the pivot with associated electrical problems, and a flexible connection where the conduit connects to the pivot support to accommodate for variations in terrain over which the system moves.
The system of the present invention overcomes these and other problems associated with prior systems in providing a pivot assembly with a structural support which in effect turns or circles about the pivot location rather than remaining pivotally stationary. Much of the design of the pivot assembly is the same as the other support towers used to support the conduit to substantially reduce cost, and is of the same width to minimize crop damage. Because the structural portion of the pivot assembly that supports the end of the conduit near the pivot location turns as the system pivots, the pivot assembly is always in alignment with the pipe for ready towing of the system by either straight towing or at an angle and regardless of its location. Because the pivot support structure pivots with the pipeline, sufficient structure for towing may be permanently included without the need to install special towing cables which must be removed for normal system operation. Its relatively light weight pivot assembly makes it possible to tow the system from either the pivot end or the outer end of the conduit. No collector ring is necessary.
The towable system of the present invention is easy to connect and disconnect at a given pivot location. The pivot assembly has a connector for pivotally anchoring the system that is movable into and out of engagement with the ground, such as a hole formed in the ground. The connector remains pivotally stationary relative to the ground, and attaches to the conduit and the liquid source for supplying liquid to the system. No elaborate preparation at the pivot location is required, and the engagement of the connector with the ground is sufficiently loose to accommodate variations in terrain over which the system operates.
These and other advantages are apparent from the drawing and detailed description to follow.